The present invention includes an idle fuel delivery system for a slide valve type carburetor. Such carburetors generally have a body defining an air induction passage, and a fuel nozzle adjacent or extending into the induction passage. The induction passage and a fuel well are connected by an orifice in the fuel nozzle. A slide valve is disposed to travel perpendicular to the induction passage and thereby produce a variable Venturi effect. Affixed to the slide valve is a tapered metering pin which extends into the orifice. Withdrawal of this tapered pin from the orifice during the operation of the carburetor increases the exposed cross-sectional area of the pin, thereby allowing a larger volume of fuel to pass from the fuel well to the induction passage for capture and mixing with the rapidly moving airstream for combustion in the engine.
Idle fuel delivery is conventionally introduced to the air passage through ports at the surface of the air passage on the downstream side of the slide valve. Idle fuel entering this air passage has close proximity to the air induction passage wall, which has a tendency to be relatively cool and therefore promotes fuel condensation. Other slide valve carburetors introduce supplemental fuel through ports in the air passage sidewall; however, the condensation problem is still present. One attempt to overcome this problem involved the collection of the condensate and its reentrainment into the airstream at a more central location in the cross section of the air passage.
A primary objective of the present invention is to achieve better fuel disbursement and consequently fuel entrainment, and thereby minimize the fuel condensation and resultant fuel losses, especially at low engine speeds.
Another objective is to eliminate the delivery of idle fuel as the carburetor attains a normal operational mode, to improve the operating economy.